This invention relates to the field of structural link strut members having aerodynamically configured cross-section.
In the ducted turbofan aircraft power plant there is need to support a large heavy object precisely located within a circumferential outer shell while also minimizing drag and turbulence in a high-velocity stream of air flowing between the large heavy object and the outer shell. In such a configuration the large heavy object is of course, a jet engine containing a plurality of bladed compressor and turbine stages while the outer shell member comprises a duct for conveying a fan-generated flow of thrust increasing air around the jet engine. The fan generating the air flow around the jet engine in such a power plant is driven from the turbine member of the jet engine. The jet engine in this arrangement is sometimes known as the core engine; the fan generating the axial airflow around the jet engine can in some ways be considered a modern-day version of the aircraft propeller--the propeller in this instance being located within a housing or fan duct.
Since the core engine in this arrangement is completely surrounded by the housing or fan duct with only a relatively small and preferably precisely defined annular space existing between the core engine and fan duct, there is need for a carefully considered suspension or structural support network connecting the core engine with the fan duct. This suspension network is called upon inter alia to physically support the core engine in a rigid manner, i.e., with no degrees of freedom with respect to the fan duct other than freedom as necessary to allow for axial thermal expansion of the core engine relative to the lower temperature fan duct. Such support must of course be capable of withstanding forces directed along a plurality of axes and oppose complex rotational or torque forces resulting from engine operation. Such a support network must also minimally impede the flow of fan air through the housing annular space. Finally, the arrangement of links in such a network must allow for radial expansion of the core engine relative to the fan duct; pursuant to this, such links are frequently skewed rather than radially oriented.
The demands on such a suspension netork, usually fabricated from an array of connecting links, are further compounded by a need for convenient adjustment of the annular space dimensions and by the need to remove portions of a power plant conveniently for maintenance and repair purposes. Since the airstream flowing axially over the core engine connecting link members can have velocities considerably greater than that of the host aircraft--velocities easily reaching the supersonic flow range, careful consideration of the connecting link aerodynamic properties is also necessary.
The patent art shows several examples of aircraft engine mounting arrangements and engine supporting members including several such arrangements expressly intended for use in jet aircraft engines. Included in this patent art is the patent of L. J. Lauck, U.S. Pat. No. 2,936,978, which concerns a rear engine mount arrangement suited for use in a turbopropeller engine and including adjustable length links or struts 76.
The patent of R. J. M. Joubert et al, U.S. Pat. No. 4,441,313, also concerns an engine mounting arrangement suitable for use with multiple flow turbojet type engines or fan type engines, and includes a pair of tie rod or link members 81.
Other jet engine mounting arrangements are shown in the patents of J. C. Anstrom et al, U.S. Pat. No. 3,085,773, wherein FIGS. 3 and 4 show the use of two types of ball or spherical elements at the ends of a strut or link member; A. Kurti et al, U.S. Pat. No. 3,243,126, which includes circular cross-sectioned expandable links 70 and 72; W. B. Campbell et al, U.S. Pat. No. 3,398,535, which shows a plurality of struts 34 supporting portions of a jet engine; A. F. Amelio, U.S. Pat. No. 3,907,220, which includes an engine mount 18 and a pair of rods 29 and 30; N. A. R. Torstenfelt, U.S. Pat. No. 4,149,826 which concerns a temperature responsive switch mount; P. Murphy, U.S. Pat. No. 4,213,585, which includes strut-like members 34, 36 and 52; and P. J. Legrand et al, U.S. Pat. No. 4,346,861, which shows a series of elaborate engine mounting structures in FIGS. 1-4.
A second group of patents is concerned with the use of differential thread arrangements in the construction of link or strut-like members. This group includes the patent of A. K. Espenas, U.S. Pat. No. 2,420,364; J. F. Grace, U.S. Pat. No. 2,485,280; M. W. Haines, U.S. Pat. No. 2,783,809; and A. Violleau, U.S. Pat. No. 3,239,930. The Violleu patent concerns a connecting rod intended for use on an aircraft in a flight control apparatus and is shown in FIGS. 1 and 2 to include end terminations having ball bearing or spherical flexible mountings and held in position with a jam nut which is secured by a bendable thin washer.
Each of the above prior patent inventions falls short of providing an improved link arrangement suitable for use in high velocity airstreams as is afforded by the combination of the present invention.